Short CommunicationDisk-based solid phase extraction for the determination of diclofenac and steroidal estrogens E1, E2 and EE2 listed in the WFD watch list by GC-MS

- The analysis of E1, E2, EE2 and DF in 10 L whole SW is reported for the first time.
- Whole samples were extracted using SPE disks on an automated SPE system.
- Successful GC-MS analysis relies on drying of the SPE disks prior to elution.
- LOQs, set by Decision 2015/495/EU, were achieved for E1 and DF, but not for E2 and EE2.
- Quantifiable amounts of DF were present in SW samples.

The aim of this study was to develop and validate an analytical method for determining estrone, 17β-estradiol, 17α-ethynyl estradiol and diclofenac in whole surface water samples at or below the limits of quantification as set out in Decision 2015/495/EU. The method is based on solid-phase extraction using Atlantic® HLB disks in a semi-automated system (SPE-DEX® 4790). The method involved extracting 10 L of whole surface water samples followed by derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide) and analysis by gas chromatography-mass spectrometry. Drying the disks overnight at 25 °C followed by elution with ethyl acetate resulted in extraction recoveries between 75.9% and 120% and limits of quantification of 0.290 ng L− 1 for estrone, 1.37 ng L− 1 for 17β-estradiol, 0.724 ng L− 1 for 17α-ethynyl estradiol and 0.119 ng L− 1 for diclofenac. Despite extracting 10 L of sample, obtained limits of quantification for 17β-estradiol and 17α-ethynyl estradiol were above those set in the Decision 2015/495/EU, while limits of quantification for estrone and diclofenac were lower. The method was applied to six Slovene surface waters, among which four contained detectable concentrations of only diclofenac (0.313 ng L− 1-5.69 ng L− 1). To our knowledge, this is the first study reporting a large volume solid-phase extraction using disks for the determination of estrone, 17β-estradiol, 17α-ethynyl estradiol and diclofenac in whole surface waters.

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